It is known in the motor vehicle and other industries that it is desirable to fill a hollow structure with a cast foam. The foam is injected into the space in its liquid state and then expands and cures to fill the hollow space. The foam can stiffen and strengthen the structure. The foam can also quiet the structure against noise transmission and vibration, and provide other advantages.
It is also known to be desirable to provide a slot in a panel that defines the hollow structure, so that a push-in type fastener can be installed for the purpose of attaching a trim panel or other component to the panel.
It would be desirable to provide a cavity within the cast-in-place foam so that a push-in type fastener can easily be installed without interference from the foam.